Ultrasound coefficient of nonlinearity imaging

Abstract

Imaging the acoustical coefficient of nonlinearity, β, is of interest in several healthcare interventional applications. It is an important feature that can be used for discriminating tissues. In this paper, we propose a nonlinearity characterization method with the goal of locally estimating the coefficient of nonlinearity. The proposed method is based on a 1-D solution of the nonlinear lossy Westerfelt equation, thereby deriving a local relation between β and the pressure wave field. Based on several assumptions, a β imaging method is then presented that is based on the ratio between the harmonic and fundamental fields, thereby reducing the effect of spatial amplitude variations of the speckle pattern. By testing the method on simulated ultrasound pressure fields and an in vitro B-mode ultrasound acquisition, we show that the designed algorithm is able to estimate the coefficient of nonlinearity, and that the tissue types of interest are well discriminable. The proposed imaging method provides a new approach to β estimation, not requiring a special measurement setup or transducer, that seems particularly promising for in vivo imaging.

Feasibility of detecting change in backscattered energy of acoustic harmonics in locally heated tissues

“…Our goal is to develop a noninvasive thermometry technique to be used during hyperthermia treatments on small animals such as mice [35], and/or in certain clinical applications such skin cancer treatment. In addition to that, higher transmit frequency enhances the generation of harmonics and increases the temperature dependence of acoustic harmonics generated [19,21]. However, short focal length of the transducer and the relatively high transmit frequency limits the penetration depth of the ultrasound beam.…”

“…Ultrasound is an alternative and potentially attractive option for thermometry since it is inexpensive, portable, non-ionizing and has fast data acquisition and image processing capabilities [1,2]. Several ultrasound-based methods have been proposed for noninvasive temperature measurement such as b (the coefficient of nonlinearity) imaging, the backscattered RF echo-shift technique, change in backscattered energy (CBE), and shear wave thermometry [1,2,[16][17][18][19][20][21][22][23][24][25][26][27][28].…”

Adaptive Ultrasound Tissue Harmonic Imaging Based on an Improved Ensemble Empirical Mode Decomposition Algorithm

“…In general, the linearity of ultrasonic transmission is relative and partial; however, the non-linearity is absolute and comprehensive, and reflects the inherent characteristics of the tissue. 2 In research and applications of ultrasonic diagnoses, the utilization of the nonlinear variation in the ultrasonic propagation in tissue and the carried diagnostic information is a topic of significant interest. 3 Tissue harmonic imaging (THI) is a technique that involves the reception and utilization of harmonic information generated by ultrasonic non-linear propagation.…”

Nonlinear ultrasonic imaging in pulse-echo mode using Westervelt equation: a preliminary research

“…In recent years, ultrasound nonlinear parameter imaging has attracted significant attention for tissue characterization purposes [1][2][3][4]. During the propagation of an ultrasound wave, the nonlinear effects, which include distortion of the waveform, harmonics generation and additional attenuation, degrade the accuracy and quality of ultrasound image [5].…”

“…Ruud et al investigated a tissue nonlinearity imaging method based on a 1-D solution of the nonlinear lossy Westervelt wave equation [4]. In that paper, acoustic nonlinear parameter b is related to the ratio of fundamental and second harmonic envelopes.…”